Two-speed power tool



March 17, 1970 w. A. BERUBE 3,500,696

TWO-SPEED POWER TOOL Filed July 25, 1968 4 Sheets-Sheet 1 Q N (O r in IE J? I IO (0 IO INVENTOR dMma/M flwd ATTORN EYS WARREN A. BERUE 4Sheets-Sheet 2 Filed July 25, 1968 INVENTOR WARREN A. BERUBE ATTORNEYSMarch 17, 1970 w. BERUBE 3,500,696

TWO-SPEED POWER TOOL I Filed July 25, 1968 4 Sheets-Sheet 5 INVENTORWARREN A. BERUBE dmwm M44,

ATTOR NEYS March 17, 1970 w, BERUBE 3,500,596

TWO-SPEED POWER TOOL Filed July 25, 1968 4 Sheets-Sheet 4 INVENTORWARREN A. BERUBE AT TO RN EYS United States Patent 3,500,696 TWO-SPEEDPOWER TOOL Warren A. Berube, Camillus, N.Y., assignor to RockwellManufacturing Company, Pittsburgh, Pa., a corporation of PennsylvaniaFiled July 25, 1968, Ser. No. 747,716 Int. Cl. F16h 3/08, 3/22 U.S. Cl.74-363 11 Claims ABSTRACT OF THE DISCLOSURE A power tool having a gearselector shiftable by manipulation of an exteriorly accessible operatorinto engagement with one of two gears to connect a rotatable toolreceiving component to the tool motor through one of two drive trainsproviding different speed ratios between the motor and the toolreceiving component. An overcenter spring arrangement keeps the gearselector in firm engagement with the gear selected for engagement bymanipulation of the operator.

The present invention relates to power tools and, more particularly, topower tools of the two-speed type. An important and primary object ofthe present invention is the provision of novel, improved tools of thetype just described.

A number of power tools of the two-speed type have heretofore beenproposed. Among these are tools disclosed in U.S. Patent Nos. 1,228,828to Sasgen, 1,475,153 to Athenas, 2,845,806 and 2,911,841 to Miller,2,899,850 to Selby, 2,942,490, 3,133,450 and 3,213,305 to Riley,3,178,855 to Enders, and 3,178,956 to Stanley.

The tools of this type heretofore proposed have several drawbacks.First, with only a few exceptions, the speed change is effected byshifting gears into and out of mesh with one another. This method ofchanging speed has obvious disadvantages.

A second drawback of most heretofore proposed tools of the type inquestion in the lack of a positive type arrangement for maintaining themovable or shiftable gears in engagement with the gears with which theyare meshed by manipulation of the speed selecting mechanism.Accordingly, the vibration generated during normal operation of such atool or a change in attitude of the tool can cause the gears to becomedisengaged, which is obviously undersirable.

To remedy this drawback devices for maintaining the gears in mesh inpositive fashion have been produced. However, these have for the mostpart employed a detent type of arrangement which has generally proved tobe unsatisfactory.

It is accordingly a further important and primary object of theinvention to provide novel, improved two-speed power tools which do notutilize the shifting of gears in changing speed and which are providedwith a mechanism capable of positively maintaining the movable speedchanging elements of the transmission in the positions to which they areshifted by manipulation of the speed selecting mechanism.

Instead of a movable gear cluster the novel two-speed tools of thepresent invention utilize a gear selector which can be shifted from oneto the other of two limit positions by manipulation of a speed selectingcontrol to drive connect one of two free-running gears to a driven shafton which they are journalled and thereby change the speed ratio of thetransmission. A novel overcenter spring 3,500,696 Patented Mar. 17, 1970arrangement keeps the gear selector in firm engagement with the gearselector by manipulation of the speed selecting control. Accordingly,the present invention eliminates the problems associated with the use ofmovable gears as well as those associated with the lack of a suitablearrangement for maintaining the speed changing elements in firmengagement with the elements with which they are engaged. I

A two-speed tool utilizing a gear selector as opposed to a shiftablegear selector has heretofore been proposed in U.S. Pataent No. 2,842,490to Riley; but this Riley tool lacks a suitable arrangement for retainingthe gear selector in the position to which it is shifted by manipulationof the operator accessible speed selector. German Patent No. 533,429discloses generally a two-speed transmission which utilizes a gearselector and has an overcenter spring for maintaining the selector inthe desired position. However, the mechanism for shifting the gearselector described in the German patent employs a crank arrangementwhich is far too unwieldy'to be used in power tools of the typecontemplated by the present invention.

From the foregoing it will be apparent that other primary and importantobjects of the present invention reside in the provision of novel,improved speed selecting mechanisms for two-speed power tools and in theprovision of tools equipped with such mechanisms.

Other important objects, further novel features, and additionaladvantages of the present invention will be come apparent from theappended claims and as the ensuing detailed description and discussionproceeds in conjunction with the accompanying drawing, in which:

FIGURE 1 is a top view of a two-speed power tool constructed in accordwith and embodying the principles of the present invention;

FIGURE 2 is a partial top view of the tool depicted in FIGURE 1 with aportion of the tool casing broken away to show the arrangement of theinternal components;

FIGURE 3 is a section through the tool, taken substantially along line33 of FIGURE 2;

FIGURE 4 is a similar view, taken substantially along line 44 of FIGURE2;

FIGURE. 5 is a view similar to FIGURE 2 with a number of transmissioncomponents removed to show a novel speed selecting mechanismincorporated in the tool;

FIGURE 6 is a perspective view of a speed selecting control and a shiftslide employed in the speed selecting mechanism;

FIGURE 7 is a perspective view of a gear selector employed in the toolof FIGURE 1;

FIGURE 8 is a perspective view of a gear employed in the tool; and

FIGURE 9 is a diagrammatic layout of a gear-type transmission employedin the tool of FIGURE 1.

Referring now to the drawing, FIGURES 1 and 2 depict a two-speed powertool 20 constructed in accord with and embodying the principles of thepresent invention. The major components of tool 20 includes a casing 22housing a motor 24 which is drive-connected through a two-speedtransmission 26 to a rotatably supported tool receiving component 28provided with an internal socket (not shown) for a drill bit or othertool and rotatably supported in casing 22 by bearings 29 and 30. Tool 20is also provided with the customary on-off switch (not shown) and with aspeed selecting mechanism 31 (see FIGURE 4) including a control knob 32exteriorly of casing 22. By manipulation of control knob 32 the speedratio of transmission 26 may be altered so that tool receiving member 28will rotate at a high speed or a low speed.

The details of casing 22 and motor 24 are of no particular consequenceas far as the present invention is concerned. Accordingly, thesecomponents will not be described further herein except in conjunctionwith the novel aspects of tool which constitute the present invention.

Referring now primarily to FIGURE 2, motor 24 is mounted in the rearsection 34 of casing 22 with its output shaft 36 extending into forwardcasing section 38 where it is rotatably supported by bearing 40. Formedon die forward end of output shaft 36 is a pinion 42 which meshes with agear 44 (see also FIGURE 9) fixed to a longitudinally extending shaft 46for rotation therewith. Ehaft 46 is rotatably supported in forwardcasing section 38 in suitable bearings (not shown).

In addition to gear 44, shaft 46 carries gears 48 and 50 {see FIGURES 4and 9). In the illustrated embodiment )f the invention gear 50 is formedon the shaft, and gear 18 is pinned or otherwise fixed to the shaft forrotation herewith.

Gears 48 and 50 mesh with gears 52 and 54 which are :'ree1y rotatable ona shaft 56 rotatably supported in forvard casing section 38 in bearings58 and 60. Also carried y shaft 56 is an integrally formed gear 62 whichmeshes vith a gear 64 fixed to tool receiving member 28 by a ialf-moonkey 66, a washer 68, and a threaded reainer 70.

Referring now specifically to FIGURE 9, it will be tpparent from theforegoing that motor 24 drives gears l8 and 50 through a train includinggear 42 on the output .haft 36 of the motor, gear 44, and shaft 46, thatgears l8 and 50in turn drive gears 52 and 54, and that the shaft $6 onwhich the latter gears are journalled is drive-coniected to toolreceiving member 28 through gears 62 and 54. The drive train betweenmotor 24 and tool receiving nember 28 is completed by coupling one ofthe two free unning gears 52 and 54 to the shaft 56 on which they irerotatably journalled. This is accomplished through a gear selector 74(see FIGURES 2, 7, and 9) which is lidably journalled on shaft 56 and isfixed to the shaft 'or rotation therewith by co-operating externalsplines 76 )II the shaft and internal splines 78 on the gear selector.

Also formed on gear selector 74 are teeth or lugs 80, vhich are adaptedto engage co-operating lugs or projecions 82 on gear 54 and lugs 84which are similarly .dapted to engage co-operating lugs 86 on freerunning ;ear 52 (see FIGURES 2 and 8).

With gear selector 74 in the left-hand limit position hown in FIGURE 2,the lugs 80 on the gear selector ngage the lugs 82 on gear 54. Motor 24accordingly .rives tool receiving member 28 through a drive trainncluding motor output shaft 36, gears 42 and 44, shaft 6, gears 50' and54, gear selector 74, shaft 56, and gears 2 and 64. Selector 74 may alsobe moved to the right as hown in FIGURE 2 to a second limit position inwhich he lugs 84 on the gear selector engage the lugs 86 on free unninggear 52. With the gear selector in this position, rotor 24 drives toolreceiving member 28 through a drive rain including the motor outputshaft, gears 42 and 44, haft 46, gears 48 and 52, gear selector 74,shaft 56, and ears 62 and 64.

As shown in FIGURE 9, gears 48 and 52 have comarable pitch diametersWhile gear 50* has a much smaller itch diameter than gear 54.Accordingly, when the latter ears are engaged in the manner justdescribed, the tool :ceiving member 28 is rotated at a relatively lowspeed 1 comparison to the speed at which it rotates when gear 2 isconnected to shaft 56 by gear selector 74 and the rive is accordinglythrough gears 48 and 52.

One of the novel and most important features of the resent invention isthe speed selecting mechanism 31 proided to move gear selector 74between its two limit posi- 4 tions to provide low and high speedoperation and to retain the gear selector in firm engagement with thegear 52 or 54 selected by manipulation of speed selecting control knob32. Referring now primarily to FIGURES 2, 4, 5, and 6, the majorcomponents of mechanism 31 are a shift slide 88, an overcenter spring90, and the control knob 32 referred to previously. Shift slide 88includes a main body portion 92 mounted for rectilinear movement along apath parallel to the longitudinal axes of shafts 46 and '56 between thetwo limit positions shown in full and dotted lines in FIGURE 5 on atrack or groove 94 formed in forward casing section 38.

Extending at right angles from the main body portion 92 of the shiftslide 88 is a bifurcated portion 95 having two arms 96 and 98 which fitinto a peripheral recess 100 in gear selector 74. Accordingly, as shiftslide 88 is rectilinearly moved from the left-hand limit position shownin full lines in FIGURE 5 to the right-hand limit position shown indotted lines in the same figure, the gear selector is moved from thelimit position shown in FIGURE 2 in which it drive connects gear 54 toshaft 56 to a limit position in which it drive connects gear 52 to thesame shaft. Similarly, shift slide 88 may be moved in the oppositedirection to disengage the gear selector from gear 52 and re-engage itwith gear 54.

The rectilinear movement of shift slide 88 just described is effected bymanipulation of control knob 32 which includes a shaft 104 extendingthrough an aperture 106 in the side wall of the casing. This rotatablysupports control knob 32 from the casing from which it is separated byO-ring 108. Control knob 32 is retained in place by a snap-in typeretainer 110 fitted in a groove 112 in shaft 104 (see FIGURE 6) with awasher 114 interposed between retainer 110 and the side wall of casingsection 38.

Carried on the inner end of shaft 104 and extending parallel to butspaced from the axis of rotation of control knob 32 is an eccentric pin116 which extends through an elongated, vertical slot 118 in the body 92of shift slide 88. As knob 32 is rotated, the shift slide moves back andforth along supporting track 94 because of the eccentric disposition ofpin 116 with respect to the center of rotation of the control knob. Asthe shift slide moves back and forth along this track, it changes thespeed of transmission 26 by engaging gear selector 74 with a dilferentone of the two free running gears 52 and 54 on shaft 56 as discussedabove.

As mentioned above, another important feature of the present inventionis a novel overcenter spring arrangement which firmly maintains shiftslide 88 in the limit position to which it is displaced by rotaton ofcontrol knob 32 and therefore maintains gear selector 74 in firmengagement with one of the two free running gears 52 and 54 despitevibration, alterations in the attitude of the tool, etc. Thisarrangement includes overcenter spring 90 (best shown in FIGURES 4 and 5which is of the conventional spring wire type. One of the two legs ofspring 90 terminates in a loop 122 fitted in a recess 124 adjacent thefree end of eccentric pin 116. A similar loop 126 at the end of theother leg of spring 90 is fitted over a projection 128 extending fromthe body 92 of shift slide 88. This provides a positive spring biasdownwardly, retaining the eccentric pin 116 in the selected position.

Referring now specifically to FIGURE 5, the operation of the shift slide88 is as follows: in order to move the shift slide 88 laterally fromeither one to the other of its two limit positions, control knob 32 ismanually rotated, moving eccentric pin 116 through approximately of arc.The initial and final portions of movement of eccentric pin 116 aremainly longitudinal in slot 118, against (or with) the bias of spring90, while the midportion of the travel of eccentric pin 116 is primarilylateral with respect to shift slide 88. Upon completion of the shift byrotation of control knob 32, it can be seen that the eccentric pin 116has moved into a latching position with respect to slot 118 and isretained there under 5. the bias of spring 90. In order to shift fromone speed to another, the eccentric pin must be moved primarilyvertically against the bias of spring 90 before any appreciable shiftingmovement of shift slide 88 takes place. As the rotation of knob 32 iscontinued with a corresponding displacement of the shift slide, spring90 exerts a force on it additive to that exerted by rotation of theknob. This snaps the slide to the limit position and, since the springexerts considerable force on the shift slide in the limit positions, theshift slide remains in these positions despite vibration, changes inattitude of the tool, etc.

From the foregoing description of an exemplary embodiment of the presentinvention, it will be apparent to those of ordinary skill in therelevant arts that. many modifications may be made without departingfrom the principles of the present invention. For example, a crank armcan be attached to the shaft 104 of control knob 32 and eccentric pin116 fastened to the end of the crank arm, if desired. These and otherchanges of a similar.

nature are accordingly fully intended to be covered in the appendedclaims to the extent that they are not expressly excluded therefrom.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The presentembodiment is therefore to be considered in all respects as illustrativeand not restrictive, the scope of the invention being indicated by theappended claims rather than by the foregoing description, and allchanges which come within the meaning and range of equivalency of theclaims are therefore intended to be embraced therein.

What is claimed and desired to be secured by Letters Patent is:

1. A power tool comprising a casing, a motor in said casing, a toolreceiving member in and rotatably supported from said casing, a firstshaft drive-connected to said motor, first and second gears havingdissimilar pitch diameters fixed to said shaft for rotation therewith, asecond shaft, third and fourth gears on said second shaft meshing withsaid first and second gears, said third and fourth gears being freelyrotatable relative to said second shaft, means drive-connecting saidsecond shaft to said tool receiving member, a gear selector slidable onsaid second shaft and rotatable therewith, co-operating means on saidgear selector and said third gear and on said gear selector and saidfourth gear for drive-connecting said selector to said third gear and tosaid fourth gear, respectively, and speed changing means including arotatably mounted two-position operator exteriorly of said casing forselectively drive-connecting said gear selector to one of said third andfourth gears when said operator is rotated to one of its two positionsand to the other of said third and fourth gears when said operator isrotated to the other of its two positions.

2. The tool of claim 1, wherein said speed changing means furthercomprises a shift slide having means connecting said gear selectorthereto, means mounting said slide in said casing for rectilinearmovement along a path parallel to that followed by the gear selector asit is shifted out of engagement with one of said third and fourth gearsand into engagement with the other of said third and fourth gears,whereby movement of said shift slide causes said gear selector to slidealong said second shaft, said operator being so connected to said shiftslide that said shift slide is displaced along said path as saidoperator is rotated from one to the other of its two positions.

3. The tool of claim 2, wherein said shift slide has an elongated slottherein and including a member carried by said operator and extendingthrough the slot in said shift slide, said operator carried member beingparallel to and spaced from the axis of rotation of said operator,whereby rotation of the operator shifts said slide along said path.

4. The tool of claim 3, wherein the slot in the shift slide extends atright angles to the path followed by the shift slide to thereby providea center position in the movement of said slide, and including anovercenter spring for maintaining said gear selector in engagement withthe gear with which it is engaged, one end of said spring being fixed tosaid shift slide and the other end of said spring being fixed to themember carried by the operator.

5. The tool of claim 2, wherein said gear selector has a peripheralrecess and said shift slide has bifurcated arms disposed in said recess,said arms extending normally from the main body portion of the shiftslide.

6. The tool of claim 1, together with overcenter spring means forretaining said operator in the position to which it is shifted andthereby keeping said gear selector in engagement with the one of saidthird and fourth gears with which it is engaged by rotation of saidoperator.

7. A power tool comprising a casing, a motor in said casing, a toolreceiving member in and rotatably supported from said casing, meansincluding a gear selector shiftable between first and second limitpositions for selectively drive-connecting said tool receiving member tosaid motor through either of two alternate gear trains with dissimilardrive ratios whereby said tool receiving member may rotate at either oftwo different speeds, and means for shifting said gear selector betweensaid limit positions comprising a shift slide having means connectingsaid gear selector thereto, means mounting said slide in said casing formovement confined to a rectilinear path, a two-position operatoraccessible from the exterior of the casing, and means so connecting saidoperator to said shift slide that, as said operator is shifted from oneto the other of its two posi tions, said slide is displaced along saidrectilinear path and said gear selector thereby shifted from one to theother of its limit positions to change the speed at which the toolreceiving member is rotated.

8. The tool of claim 7, wherein said shift slide has an elongated slottherein and said operator is rotatably journalled in said casing andincluding a member carried by said operator and extending through theslot in said shift slide, said operator carried member being parallel toand spaced from the axis of rotation of said operator, where-by rotationof the operator shifts said slide along said path.

9. The tool of claim 8, including an overcenter spring for maintainingsaid gear selector in engagement with the gear with which it is engaged,one end of said spring being fixed to said shift slide and the other endof said spring being fixed to the member carried by the operator.

10. A power tool comprising a casing, a motor in said casing, a toolreceiving member in and rotatably supported from said casing, meansincluding a gear selector shiftable between first and second limitpositions for selectively drive-connecting said tool receiving member tosaid motor through either of two alternate gear trains with dissimilardrive ratios whereby said tool receiving member may rotate at either oftwo different speeds, and means for shifting said gear selector betweensaid limit positions comprising a two-position operator exteriorly ofthe casing, means in said casing operatively connected to said operatorand said gear selector for moving the gear selector from one to theother of said limit positions as said operator is shifted from one tothe other of its two positions, and an overcenter spring operativelycoupled to said operator and to the means for moving the gear selectorfor maintaining said gear selector in the limit position to which it ismoved by the manipulation of said operator.

11. The tool of claim 10, wherein the means for moving said gearselector between said limit positions comprises a shift slide havingmeans connecting said gear selector thereto, means mounting said slidein said casing for movement confined to a rectilinear path, and means soconnecting said operator to said shift slide that, as said operator isshifted from one to the other of its two positions, said slide isdisplaced along said rectilinear path and said gear selector therebyshifted from one to the other of its limit positions, saidlast-mentioned means including a member carried by said operator andextending through a slot in the shift slide, and wherein one end of saidovercenter 7 8 spring is fixed to said shift slide and the other end ofsaid FOREIGN PATENTS spring is fixed to the member carried by theoperator. 1 019 O5 4 H1953 France References Cited ARTHUR T. McKEON,Primary Examiner UNITED STATES PATENTS 5 U.S. C1. X.R. 2,068,869 1/1937Rauen 74-343 X 74 342 2,778,237 1/1957 Romi 74342 X UNITED STATES PATENTOFFICE H CERTIFICATE OF CORRECTION Patent No 0 3 ,500 ,696 March 17 1970Warren A. Berube It is certified that error appears in the aboveidentified patent and that said Letters Patent are hereby corrected asshown below:

after "are" insert the line 40,

should read is line 47, "underline 49, "produced" Column 1, line 29,111", second occurrence, sirable" should read undesirable should readproposed Signed and sealed this 6th day of October 1970.

(SEAL) Attest:

WILLIAM E. SCHUYLER, JR

Edward M.'Fletcher, Jr. it"

Cornmissioner of Patents Attesting Officer

